The present invention relates generally cathode ray tubes, and more particularly to a cathode ray tube including a saddle type of horizontal coil used in a deflection yoke.
An important aspect of performance for a television monitor is its ability to correctly align the individual color components (red, green and blue). Convergence describes how far apart the three electron beams spread from one another within a pixel. Ideally, the beam hits all three dots in the group without hitting any adjacent groups. Mis-convergence is a quantitative measurement of the lack of convergence of the three electron beams. The resulting image will have a shadowed appearance in case of mis-convergence.
A deflection yoke is used to control the convergence of the three electron beams (red, green and blue) in a cathode ray tube (CRT) by changing the winding distribution in the horizontal and vertical coils to compensate for mis-convergence. For example, U.S. Pat. No. 5,838,099 discloses one such deflection yoke, which can be seen in FIG. 7, which depicts a perspective view showing a pair of saddle type horizontal deflection coils.
Referring to FIGS. 1A and 1B, depicted therein are two possible patterns of mis-convergence. In FIG. 1A, the mis-convergence is referred to as XH mis-convergence, whereas in FIG. 1B, the mis-convergence is referred to as HCR mis-convergence. In XH mis-convergence, the plus patterns of the red (R) and blue (B) lines fail to converge. In HCR mis-convergence, the plus patterns of the green (G) lines fail to converge with the plus patterns of the red (R) and blue (B) converged lines.
The trend in cathode ray tubes is towards larger and flatter screens. As the screen in a CRT becomes larger and flatter it becomes more difficult to adjust the mis-convergence using conventional methods.
FIG. 2A depicts a cathode ray tube exhibiting both XH and HCR mis-convergence. Note that the red (R) and blue (B) plus patterns fail to converge by about 1.0 mm and the green (G) plus patterns fail to converge with the red (R) and blue (B) plus patterns by a similar amount.
Correcting only the XH mis-convergence so that the XH mis-convergence becomes zero, results in an HCR mis-convergence of about 0.75 mm, as depicted in FIG. 2B. Alternatively, correcting the HCR mis-convergence until it becomes zero results in an over-correction of the XH mis-convergence to result in an XH mis-convergence of about xe2x88x923.0 mm., as depicted in FIG. 2C. The end result is that using conventional attempts to correct XH and HCR mis-convergence simultaneously is difficult due to the sensitivity of the winding distribution between XH and HCR mis-convergence.
One attempt to correct both of these phenomena requires extra corrective parts on the distribution yoke. For example, U.S. Pat. No. 5,142,205 discloses a deflection yoke having a correction circuit for correcting horizontal and vertical mis-convergence. This technique requires additional electronic components, thereby increasing the parts and assembly costs of the CRT and as well as increasing the overall dimensions of the resulting device.
Alternatively, the horizontal coil can be re-manufactured in an attempt to simultaneously reduce the mis-convergence phenomena. However, this becomes difficult in a fast assembly process.
The present invention is therefore directed to the problem of developing a method and apparatus for adjusting XH and HCR mis-convergence in a cathode ray tube, which method and apparatus can be employed in larger and flatter CRT screens without increasing the costs or size of the device.
The present invention solves this problem by providing a triangular cutout portion in the winding distribution disposed at a disposition angle of approximately 10 degrees relative to a horizontal axis and having a base ranging from approximately 3-15 mm.
According to one aspect of the present invention, a deflection yoke for deflecting electron beams of a color cathode ray tube includes a saddle type horizontal deflection coil, which has a front bend section and a neck bend section. The neck bend section includes a pair of openings in the winding distribution. Each of the openings is disposed at a disposition angle relative to a horizontal axis through the neck bend section of approximately ten degrees and at a predetermined distance from a center of the neck bend section.
According to another aspect of the present invention, in the above deflection yoke the predetermined distance falls within a range from approximately three millimeters to approximately fifteen millimeters.
According to another aspect of the present invention, in the above deflection yoke each of the openings has a base that lies on the disposition angle.
According to yet another aspect of the present invention, in the above deflection yoke each of the openings has a substantially triangular shape.
According to yet another aspect of the present invention, in an alternative embodiment of the above deflection yoke each of the openings has a substantially trapezoidal shape.
According to yet another aspect of the present invention, in an alternative embodiment of the above deflection yoke each of the openings has a substantially semicircular shape.
According to another aspect of the present invention, a method for simultaneously correcting XH and HCR mis-convergence in a deflection yoke of a cathode ray tube, which deflection yoke has a horizontal coil that includes, a front bend section and a neck bend section, includes three steps. First, a pair of voids is created in a winding distribution in the neck bend section of the horizontal coil. Second, the pair of voids are disposed at a disposition angle of approximately ten degrees, wherein the disposition angle is defined relative to a horizontal axis through the neck bend section of the horizontal coil. Third, a width of each of the voids is adjusted so that a resulting XH and HCR mis-convergence curve passes through the origin.
According to another aspect of the present invention, in the above method the width of each of the voids is adjusted within a range from approximately three millimeters to approximately fifteen millimeters.
According to yet another aspect of the present invention, in the above method each of the voids is disposed so that their base lies on the disposition angle.
According to another aspect of the present invention, in the above method each of the voids is created with a substantially triangular shape.
According to yet another aspect of the present invention, in an alternative embodiment of the above method each of the voids is created with a substantially trapezoidal shape.
According to yet another aspect of the present invention, in an alternative embodiment of the above method each of the voids is created with a substantially semicircular shape.
According to another aspect of the present invention, a device for self-correcting mis-convergence of electron beams of a color cathode ray tube includes a horizontal coil with a neck bend section.and a front bend section. The neck bend section has a winding distribution symmetric about a horizontal axis. In addition, the device includes a means for simultaneously correcting XH and HCR misconvergence. The correcting means is disposed in the neck bend section and creates a XH-HCR misconvergence curve for the device that passes through the origin.
According to another aspect of the present invention, in the above device the correcting means includes a pair of openings in the winding distribution of the horizontal coil.
According to another aspect of the present invention, in the above device each of the openings is disposed at a disposition angle relative to the horizontal axis through the neck bend section of approximately ten degrees.
According to another aspect of the present invention, in the above device each of the openings is disposed at a predetermined distance from a center of the neck bend section.
According to another aspect of the present invention, in the above device the predetermined distance falls within a range from approximately three millimeters to approximately fifteen millimeters.
According to another aspect of the present invention, in the above device each of the openings has a base that lies on the disposition angle.
According to another aspect of the present invention, in the above device each of the openings has a substantially triangular shape.
According to yet another aspect of the present invention, in an alternative embodiment of the above device each of the openings has a substantially trapezoidal shape.
According to yet another aspect of the present invention, in an alternative emodiment of the above device each of the openings has a substantially semicircular shape.